The present invention to a light-tight tearable covering for a stack of photographic or X-ray sheet films for inserting into a supply magazine of a sheet film cassette-loading device. Such a supply magazine is provided on its side opposite to the tearable covering side with a pulling device, for example a winding device for removing the covering by engaging a winding flap after closing the supply magazine, and a wrapping closure flap of the covering is releasably held on a flat side of the covering.
Sheet film stacks with such coverings are commercially available. The covering must be opened in a dark chamber and the film pack removed from the covering must be inserted in the supply magazine. However, it is now desired to introduce the film pack arranged in the covering during daylight in the supply magazine in a light-tight manner, and after closing the magazine to open the covering and to pull out the film pack.
A supply magazine of this type is disclosed for example in the German document DE-GMS 7,725,804. The tearable flap of the covering is formed by the labyrinth-like mutually folded ends of the flat sides of the covering. Under the action of the pulling which the winding device applies during turning upon the winding flap, the folds must be torn from one another, so that the covering is pulled from the stack during a further turning of the winding device and pulling-on. It has been determined that the forces to be applied on the winding device are not sufficient to tear the tearable flaps from one another in an efficient manner. Therefore, this known arrangement is not suitable for daylight operation, or in other words, for loading the magazine and opening the covering in the closed magazine.
A supply magazine of a similar type is disclosed in the German document DE-PS 3,405,423. The type of the magazine shown here cooperates for opening of the stack covering with the device in which the magazine must be used, and therefore, can be used only in the specially designed device and not universally. In another magazine described here, the conditions are the same as in the magazine in accordance with the German document DE-GM 7725804 with the difference that the folded tearing flaps of the covering must be removed not during winding of the winding flap, but instead by pulling off the winding flap manually. The force for tearing the folded tearing flaps cannot be reached practically.
The German document DE-OS 3,543,024 discloses a supply magazine which has a blade like or saw-like tearable strips for the tearable flaps of the film pack covering after the closing of the magazine. This construction not only requires additional expenses for the supply magazine. It also has the disadvantage that a daylight loading is possible only with specially designed magazine, while the film pack for loading of the different types of known magazines, for example the one disclosed in the German document DE-GMS 7,725,804, cannot be used during daylight.
Finally, the German reference DE-PS 3,612,710 discloses coverings of the above mentioned type in which at least one strong tearable flap which requires high pulling force due to the weight of the stack is removable by hand. They are arranged between or under the holding strips which are brakeable by application of a pulling force to the closure flap or covering. This construction is expensive because of two different adhesive connections, namely differently strong adhesive connections, and their arrangement relative to one another.